In an endless sea of sand drifts the Mud Whale, a floating island city of clay and magic. In its chambers a small community clings to survival, cut off from its own history by the shadows of the past.

The battle for the Mud Whale becomes a deadly rout as the Marked fight to protect their home and their comrades from the invading apátheia soldiers. Meanwhile, Chakuro and the rest of the boarding party have made it safely onto the imperial battleship Skyros, but their mission turns bloody when they reach the thymia-proof chamber at the heart of the ship. How will they destroy the enemy Nous and save the Mud Whale without access to their powers?